Simple diaphragm shut-off valves are well known in the prior art and typically employed to control a water supply, such as in a washing machine or the like. More particularly, in controlling the supply of water to a tank or to the reservoir of a chamber pot, it has been known to use a float valve. Such a float valve is coupled to a lever mechanism for controlling the supply of water in response to the level of water in the tank or reservoir.
The prior art diaphragm shut-off valves are deficient in that, because the valve operates in response to a differential pressure on opposite sides of the valve, a water hammer effect is generated whenever the water supply is shut-off. Further, the float valve of the prior art contributes to the water hammer effect because the float valve ultimately controls an outlet itself which shuts off water supply. Further, the prior art float valves have heretofore required a large float and a relatively long lever in order to generate a large enough force. Such large float and long lever requirements require a relatively large space in which to install them and a large force to properly operate them. Additionally, the float valve and lever linkage, because of the harsh operation environment, is required to be fabricated with precision, and out of durable and corrosion resistant materials.
The prior art has attempted to address the water hammer problem inherent with diaphragm shut-off valves, as illustrated in the U.S. Pat. No. 3,672,627. In this reference, a diaphragm shut-off valve responsive to differential impressure includes a plastic insert comprising a necked portion of the diaphragm entering into a fluid outlet. The necked portion causes a throttling effect of the fluid flowing therethrough, and thereby purports to reduce the water hammer effect.
In the Japanese Utility Model Provisional Publication No. 54-40520, a tapered part is inserted into the fluid flow outlet. This tapered part causes a gradual reduction in the velocity of the fluid flow, and thereby purports to eliminate the water hammer effect. Nevertheless, there have remained problems in the prevention of the water hammer effect which have not been adequately solved. Particularly, when the closing velocity of the shut-off valve is rapid at high fluid pressures, the attempted solutions to the water hammer effect have been ineffective.
The prior art has suggested that the water hammer problems can be solved if the closing velocity of the diaphragm valve is gradually reduced. Heretofore, in very large differential pressure valves, a form of damper has been installed in the concentric shaft of the diaphragm shut-off valve for the purpose of reducing the closing velocity of the shut-off valve. However, this form of damper has been impossible or very impractical to install in small sized differential pressure valves due to structuring problems, economy, etc.